This invention relates to the genetic alteration of the metabolism of cells to carry out a desired bioconversion, specifically enhanced nitrite production.
Nitric oxide (NO) has drawn increasing attention for its roles in the vascular, digestive, immune and nervous systems. In these systems NO results, along with its spontaneous oxidation products NO.sub.2.sup.- and NO.sub.3.sup.-, from the deimination of L-arginine by an NO synthase (NOS). Two isozymes of NOS have been described in various cell types; a mildly active constitutive NOS (cNOS) and a highly active endotoxin and cytokine inducible NOS (iNOS). Both iNOS and cNOS have been identified in macrophages.
NO has been identified as the endothelial- and neutrophil-derived relaxing factor for vascular smooth muscle cells. Additionally, NO is thought to act as a neurotransmitter or second messenger largely because of its rapid diffusion through cell membranes and ability to increase cGMP levels in affected cells. In the immune system, production of NO, NO.sub.2.sup.- and NO.sub.3.sup.- by phagocyte iNOS requires stimulation from specific ligands such as lipopolysaccharide (LPS) or interretort (IFN). Oxidized nitrogen species are generated by phagocytges as nonoxidative microbicidal, tumoricidal, or inhibitory agents.
The importance of oxidized forms of nitrogen is apparent. Unfortunately, study of NO and NO.sub.2.sup.- is hampered by the short-lived, highly reactive nature of these molecules in biological systems. NO exists as a minor equilibrium product of the breakdown of nitrous acid (the aqueous form of NO.sub.2.sup.-) as in the following equation: EQU 3 HNO.sub.2 .revreaction.HNO.sub.3 +2 NO+H.sub.2 O
Hence, development of cell lines which express high levels of these molecules upon induction and in a highly regulatable manner is desirable to further elucidate their roles in cell biology. Also, leukocytes producing high levels of nitrite would be useful as highly regulatable tumor killing agents.
Accordingly, it is an object of the present invention to provide cell lines capable of enhanced nitrite production.
Other objects and advantages of the invention will be apparent to those skilled in the art.